Frequency modulation



July 3, 1945. H. TuNlcK FREQUENCY MODULATION Filed March 2'7.' 1942 2 sheds-sheet 1 x k um xx xbm July 3 1945. H. TUNlcK FREQUENGY'MODULATION 2 sheets-sheet 2 Filed March 27, 1942 .MSU

INVENTOR #weer fan/cx B* )#54 AT'TORNEY vformerTFII upon land line LLII.

Patented July 3, 1945 l Price FREQUENCY MonULA'rloN Harry Tuniek, Rye, N. Y., assignor to Radio-Corporation of America, a corporation of Delaware Application March 27, 1942, Serial No. 436,423

.14 claims. '(cl. 17a-ss) This is a continuation in part of m'y copending application Serial No. 369,800, filed December 12, 1940, vnow United States Patent No. 2,282,102.

My present'invention relates to signaling by means of frequency modulated waves. An object of my present invention is to provide improved circuits especially adapted for telegraphio and telephonie communication by frequency shifted of my present invention 'will be self-evident as the more detailed description thereof proceeds,

In .the accompanying drawings:

Fig. 1 is a wiring diagram of a frequency modulation transmitter employing principles""of my present invention and which is especially adapted for telegraphy; and

Figs. 2 and 3y are wiringdiagrams of modifica.-

tions useful for either telegraphy or telephony.

In Figure 1 manipulation of the key KII impresses tones from the audio oscillator TII or from the audio oscillator TI2 through trans- Filter FII Waves. Other objects', advantages -and features. v

passes audio tone TII of frequency FI generated by oscillator TII and'iilter FIZ passes the tone of audio frequency F2 generated by oscillator Tl2 into the rectiers Ril, Rl: to which the filters are respectively connected. The rectified tones' move key KI2 up ordown, putting the inductive reactance XII or capacitive reactance XI2 eil'ectively into circuit with the electrodes of reactance tube TRM. v

Oscillator 0I I, of the Hartley type, is thereby Figure 1, but which, for the sake of simplicity, has not been duplicated in Figure 2`.

With key 'KI2 of Figure 2 in its left-handcon# tacting position, the lower sectionof the multi- Velement tube'MT is permitted to draw current and thereby eectively short-'circuits condenser CI4 and makes the effective feedback path from the plate tothe grid of reactance tube TRI! through inductance XI4. Similarly, when key K12 of. Figure 2 is moved to its right extreme position, the` upper grid-of tube MT causes the upper section of the control tube MT to become conductive,

thereby effectively short-circuiting reactance XI4 and making the effective feedback path through the capacitive reactance CI4. AIn this way, the

effective reactance of tube TRI2 is changed,

thereby changing the frequency of the vacuum tube oscillator VTO to which it is connected, as

illustrated.

A multiplicity of tones or a complex wave, such as voice, may be used in thel system of Figure 2` These complex tones orl voice waves with or without amplication are fed through transformer 'I'FI2- in phase opposition to the grids GG, as shown. When this is done, of course, key KI! is left in its open mid-position as shown.

lResistors 6I) and 62 of Figure 2 'prevent shortcircuiting of battery .BXIZ during keying of key KI2 with its contacts. If desired, an additional 30 batteryBXl3v may be connected as shown Ain the y lead to key KIZ.

varied in frequency from one value to another depending upon whether reactive inductance XI I or capacity X I2 is connected in the circuits. It. will be appreciated that condenser CII is merely y a large by-passing condenser. Resistance 40 is of low value relative to the reactance of either XII or XI2. Resistors 42, 44 are cathode return biasing resistors, condensers 46,48, Wand 52 are radio frequency by-pas's condensers, and condenser 54 Resistance 12 is of. relatively low value "with respect to the relative high inductive reactance of XI4 or the relatively high capacitive reactance vCI'4. .Resistor 14 is a cathode return biasing re sister. Condensers BCI8, B020, BC22, B024, BCH, BCI4, BCIG. and BCIB are large bY-Pass condensers. Condenser C10 is a tuning condenser.

Fig. 3 is similar to Fig. 2, but it willbe'noted that tlie reactance tube circuits have been modiis the usual tuning condenser. The other portions ofthe circuit of Figure 1 are deemed to be self-explanatory to those skilled in the art.

In the system of Figure 2, the reactance tube TRI! has its plate interconnected with its grid through the large by-passing condenseLBC I 2, in-- Aductive reactance XI4 and capacitive reactance CI4.V The'multi-element tube MI' is provided,

the grids G of which are biased to cut-off by means of biasing source; BXI2. The'key KIZ; as in connection vwith Figure 1, maybe actuated electromagnetically by means o f coils ECII vand ECI2 connected to recti'ilers such as RII, ARI2 and the system to the left thereof as shown in 66 Figure 3 is similar to Figure 2, In Figure 3.

In Figure 1 when the capacitive reactance XI2 is connectedbetween the plate and control grid,

tube 'I'RII -appears as a capacitive reactance across the tuned circuit of the oscillator, thereby lowering the frequency ofoscillations generated. When inductive reactance XII is effectively connected between the plate and grid ofreactance tube TRII, the reactance tube acts as an inductance in shunt to a portionfof the tuned tank circuitof oscillator tube OII thereby lowering the effective inductance and raising the frequency of oscillations generated.

however, the reactances XH and C14 are eiec-` tively connected between the control grid and cathode of reactance tube TRW, whereas in Figshort circuited'and capacitive reactance CH is effectively connected between the control grid and cathode of -reactance tube 'I'Rl2,' the latter acts as an inductive reactance in parallel to a portion o! the tank circuit of oscillator VTO, thereby effectively reducing the inductive reactance of the tank circuit of the oscillator and thereby efiectively raising its operating frequency. Similarly, when condenser C H is effectively short circuited out of circuit and coil XII is eiiectivell1 connected between the grid and cathode of reactance tube TRIZ, the frequency or operation of oscillator VTO will be lowered.' s

Although the various reactance tubes have been illustrated as screen grid tubes, they may, of course, be pentodes, in which case the fifth electrode is connected in the usual way directly to the cathode. i

Having thus described my invention what I claim is: Y i

1. In combination, an oscillation generator, a reactance tubeoperatively rassociated with said generator, said reactance tube having an anode, a cathode and a control electrode,an inductive phase shifting reactance, a capacitive phase shifting reactance, an unbypassed resistor having a low value with respect to either of said reactances effectively connected between said control electrode and cathode, and a keying circuit for keying either the inductive reactance or the capacitive reactance selectively into circuit between lsaid anode and control electrode;

2. In combination, an oscillation generator, a4 reactance tube having an fanode electrode, a cathodeelectrode and a control electrode for changing the frequency of oscillation of said oscillation generator, said reactance tube havingV its anode and cathode connected to a frequency determining circuit of' said generator, a phase shifting inductive reactance, a phase shifting capacitive electrodes.

3. A reactance tube circuit comprising `a reactances of opposite sign connected between a pair of electrodes of said reactance tube, a resistance ci relatively high value with respect to the value of reactance of either o! said reactances eirectiveu ly connected between another pair oi electrodes of said reactance tube, and a circuit for variably shunting said reactances out ot and into circuit.`

5. A reactance tube circuit comprising a tube having an anode, a cathode and a control electrode, a pair of serially connected phase shifting reactances connected between a pair of electrodes of said reactance tube, a resistor having a high value or resistance with respect to 'the value or reactance of either of said phase shifting reactances effectivelyconnected between another pair of electrodes of said reactance tube, an electron discharge device circuit effectively in shunt to one of said reactances, an electron discharge circuit effectively in shunt tothe other of said reactphase shifting reactance, an unbypassed resistor eiectively in series with said reactances, said resistor being effectively connected between a pair of said electrodes of said reactance tube, and a keyingcircuit for selectively keying said reactancesvibetween another pairt of electrodes of said reactance tube'.

'7. A reactance tube circuit comprising a reactance tube having an anode electrode, a `cathode electrode, and a control electrode, a pair of serially connected reactances of opposite sign effectively connected between the anode electrode and control electrode of said reactance'tube, a resistance of relatively low value with respect to the value of reactance of either of said reactances eff ectively connected between the control electrode and cathode electrode of said reactance tube, and a circuit for selectively short-circuiting either of said reactances.4 l

8. A reactance tube circuit comprising a reactance tube having an anode electrode, a cathode electrode, and a. control electrode, a pair of serially connected reactances of opposite sign effectively connected between the control electrode and the cathode electrode of said reactance tube, a resistance of relatively high value with respect s tothe value of reactance of either of said reactances eectively connected between another pair of electrodes of said reactance tube, and a circuit for selectively short-circuiting either of said reactaces. v.

9. A. reactance tube circuit comprising a tube I having an anode, a cathode. and a control elecance tubelhaving an anode, a cathode and a control electrode, a pair of serially connected reactances of opposite sign connected between a pair of electrodes of said reactance tube, a resistance y an electron discharge circuit effectively in shunti to the other oi said reactances, and circuits forv 4. A reactance tube circuit comprising a reactance tube having an anode, a cathode and a control electrode, a pair of serially connected reacttrode, a pair oi' serially connected phase shifting reactances eiectivelyconnected between the-control electrode and cathode of said reactance tube,

a. resistor having a high value of resistance withrespect to the value of reactance of either of said phase shitting reactances eiiectively connected between the anode and control electrode or said reactance tube, an electron discharge device circuit effectively in shunt to one of said reactances,4

varying the conductivities or. said electron discharge device circuits.

10. In combination, an oscillation generator, a

Vreactance tube having anode, cathode and control electrodes, said reactance tube heaving its anode and cathode effectively connected to a frequency determining circuitof said`generator, an inductive phase shifting reactance, a capactive phaseshifting.reactance, a resistor having a high value with respect vto the value of reactance of either of said reactances, said resistor being effectively connected between said anode electrode and said control electrode of Asaid reactance tube, and a keying circuit for selectively keying said reactances effectively into circuit between said control electrode and said cathode electrode of said react-ance tube. I

11. A reactance tube circuit comprising a reactance tube having an anode, a cathode and a control electrode, a pair of serially connected reactances of opposite sign eiectively connected between a pair of electrodes of saidv reactance tube, aresistance oi relatively low value with respect to the value of reactance of either of said reactances effectively connected between another pair of electrodes of said reactance tube, and a circuit for selectively short-circuiting either vof said reactances.

12. A reactance tube circuit comprising a reactance tube having an anode, a cathode and a control electrode, a pair of serially connected reactances of opposite sign effectively connected between a pair ci electrodes of said reactance circuit for variably shunting said reactances out of andvinto circuit. v y

13. A reactance tube circuit comprising areactance tube having an anode electrode. a cathode electrode and a control electrode, a pair oi serially connected reactances of opposite sign efreactances effectively connected between the antube, a resistance oi' relatively low value with respect to the value of reactance oi either of said reactances eiectively connected between another pair of electrodes of said reactance tubel and a ode and control electrode of said reactance tube,

a resistor having alow value of resistance with respect to the value of reactance of either of said phase shifting re'actances effectively connected between the control electrode and cathode oi said reactance tube, an electron discharge device circuit eiiectively in shunt to one of said reactances. a-nelectron discharge device circuit eiectively in shunt to the other of vsaicl reactances, and circuits for varying the conductivities of said electron discharge device`circuit.

- HARRY TUNICK. 

